Welsh Secretary David Jones remained under pressure over comments about gay marriage today as Labour dismissed his denial of being homophobic and demanded a public apology.

Mr Jones insisted he was not opposed to same-sex couples raising children after sparking outrage by appearing to suggest they could not provide a "warm and safe environment".

"I did not say in the interview that same-sex partners should not adopt children and that is not my view," said the MP - who had been explaining his decision to vote against the legalisation of gay marriage.

"I simply sought to point out that, since same-sex partners could not biologically procreate children, the institution of marriage was one that, in my opinion, should be reserved to opposite sex partners."

"I made the point of stressing that I was fully supportive of committed same-sex relationships. I also strongly approve of civil partnerships," he added in a statement.

In the original interview - with ITV Wales - he said the institution of marriage was meant to provide "a warm and safe environment for the upbringing of children, which is clearly something that two same-sex partners can't do.

"Which is not to say that I'm in any sense opposed to stable and committed same-sex partnerships," he said, adding that he had "people in my life who are important to me who are gay".

Shadow Welsh secretary Owen Smith has written to David Cameron dismissing the explanation as "obfuscation" and calling on the Prime Minister to demand his cabinet colleague withdraw the remark and apologise.

In the letter, he said the remarks "betray a lack of acceptance for same-sex relationships that is out of step with the majority of people in our country.

"I believe you should now ask him to withdraw the comments and apologise. I would also like to ask whether you find it acceptable or appropriate for the most senior Conservative MP in Wales to make these comments?" he added.

Mr Smith said: "David Jones has chosen not to apologise for these unacceptable comments. It is time for David Cameron to make clear whether he thinks it is unacceptable for the Welsh Secretary to make these comments."

A spokesman for Mr Cameron said last night: "Gay marriage and gay adoption are both conscience issues and, as such, have been treated as free votes. The Prime Minister is a supporter of both."